Immunological functions display aging-associated defects such as decreased reactivity to antigen by T cells. We hypothesize that functional differences between equivalent cell populations from young and old animals will manifest themselves in altered gene expression phenotypes. To test this hypothesis we will employ DNA microarrays that allow to study thousands of transcripts in parallel. Due to the complexity and cost of both the technology and the analysis tools needed to interpret the data, microarray expression analysis is difficult to implement and support at the level of the individual laboratory. Therefore, we will centralize expression profiling in a core for gene expression profiling. This core will work together with the Gene Microarray Shared Resource (GMSR) of OHSU thus leveraging existing resources at this well established service center. We will perform gene expression profiling for projects by Lewinsohn, Nikolich-Zugich, and Picker using human cDNA arrays containing approximately 8900 different clones printed by the GMSR. Array analysis will encompass isolation of RNA from selected celt populations, RNA amplification, labeling and hybridization. Data quantitation and normalization will be performed in comparison to a universal reference derived from peripheral blood mononuclear cells of unrelated rhesus macaques. Data analysis of microarray results will be supported by the Biostatistics and Bionformatics Core which is an extension of the bioinformatics unit of the GMSR. We expect to detect statistically significant transcriptional changes in aged versus young T cells and antigen presenting cells. Transcripts changing most significantly will be selected for confirmation by quantitative PCR in an unrelated groups of rhesus macaques. The results are expected to identify profiles that reflect the aging process in these cells and might thus be linked mechanistically to the observed defects in immune responses.